A plan now before Congress would create a national park spread over three states to protect the aging remnants of the atomic bomb project from World War II, including an isolated cabin where grim findings threw the secretive effort into a panic.

Scientists used the remote cabin in the seclusion of Los Alamos, N.M., as the administrative base for a critical experiment to see if plutonium could be used to fuel the bomb. Early in 1944, sensitive measurements unexpectedly showed that the silvery metal underwent a high rate of spontaneous fission - a natural process of atoms splitting in two.

That meant the project's design for a plutonium bomb would fail. J. Robert Oppenheimer, the project's scientific head, was so dismayed that he considered resigning.

But he and his colleagues pressed ahead with a new design. On July 16, 1945, the world's first atom bomb - a lump of plutonium at its core - illuminated the darkness of the central New Mexican desert with a flash of light brighter than the sun.

The plan for a Manhattan Project National Historical Park would preserve that log cabin and hundreds of other buildings and artifacts scattered across New Mexico, Washington and Tennessee - among them the rustic Los Alamos home of Oppenheimer and his wife, Kitty, and a large Quonset hut, also in New Mexico, where scientists assembled components for the plutonium bomb dropped on Japan.

"There is no better place to tell a story than where it happened," Jarvis said in a statement. "The National Park Service will be proud to interpret these Manhattan Project sites and unlock their stories in the years ahead."

But critics have faulted the plan as celebrating a weapon of mass destruction, and have argued that the government should avoid that kind of advocacy.

Historians and federal agencies reply that preservation does not imply moral endorsement, and that the remains of so monumental a project should be saved as a way to encourage comprehension and public discussion.

Supporters of the atomic park are pressing for a vote on the measure in the expiring 112th Congress. The House, influenced by the critics, rejected the plan in September, and advocates are re-engaging members with new arguments in an effort to tip the balance of opinion in their favor.

"Both the House and Senate had hearings," Kelly said in an interview. "We're guardedly optimistic."

The bills are sponsored by a bipartisan group of 10 lawmakers, mainly from the three states, led in the Senate by Jeff Bingaman, D-N.M., and in the House by Doc Hastings, R-Wash.

In 2001, the council's panel of distinguished experts recommended that the sites be established "as a collective unit administered for preservation, commemoration, and public interpretation in cooperation with the National Park Service."

In 2004, Congress directed the secretary of the interior to study the park's feasibility, in consultation with the secretary of energy. Last year, Ken Salazar, the interior secretary, wrote to Congress recommending its establishment.

He called the bomb's development "one of the most transformative events in our nation's history," noting that it ushered in the atomic age, changed the international role of the United States and helped set the stage for the Cold War.

Supporters of the park argue that preserving and managing the atomic sites is Washington's least expensive option. Five years of National Park Service care, they say, would cost $21 million; demolishing the buildings and atomic sites would run to $200 million.

Kelly, of the Atomic Heritage Foundation, said the overall goal was commemoration, not celebration. She argued that even regrettable aspects of history - like the Native American massacres and Civil War battles - deserved site preservation and cultural remembrance.

"This is a major chapter of American and world history," she said. "We should preserve what's left."